Telephone-transmitter



J. H. IRWIN. Telephone-Transmitter.

No. 223,352. Patented Jan. 6,1880.

fittest:

N.PEYF.RS. PHOTO-LITMOGRAPHER, WASHINGTON. D. C.

UNITED STATES PATENT OFFICE.

JOHN H. IRWIN, OF PHILADELPHIA, PENNSYLVANIA.

TELEPHONE-TRANSM ITTER.

SPECIFICATION forming part of Letters Patent No. 223,352, dated January 6, 1880.

Application filed January '21, 1879.

To all whom it may concern Be it known that I, JOHN H. IRWIN, of Philadelphia, county of Philadelphia, State of Pennsylvania, have invented a new and useful Improvement in Telephones; and I do hereby declare that the following is a full, clear, and exact description of the same.

This invention relates to that class of acoustic telegraphs heretofore patented to me, wherein the sensitive point, where vibrations of the material of the apparatus produced by sound- Waves are transformed into undulations of an electric current capable of exciting in a proper receiving-instrument similar vibrations and the reproductions of similar sounds, consists of two surfaces in contact, and delicately adjusted by an elastic suspensory support.

The object of the present improvement is to increase the sensitiveness of the transmitter; audit consists in a thin plate of elastic ma terial placed in the base of the instrument, secured at one or more of its edges only, and supporting carbon or its substitute, against which the suspended part rests.

That others may fully understand my improvement, I will particularly describe it, having reference to the accompanying drawings, wherein- Figure l is a perspective view of my instrument. Fig. 2 is a sectional elevation of the same.

For convenience, I show in the principal figure an instrument of the form heretofore patented to me, though I do not design to limit myself to the particular structure of the instrument so shown, but only within the scope of the several improvements invented and I heretofore patented by me.

or frame, B, to support the end of the suspension-spring G and adjusting device D.

E is the needle, suspended by the spring (3, with its free end in contact with the carbon F. The needle E, through its spring 0 and a connecting-wire, is joined to one of the bindingscrews, and the carbon F is similarly coupled with the other binding-screw, so that the battery-current passes the point of contact between E and F, and is transformed into a series of undulations by the varying resistance when the instrument is caused to vibrate by impact of sound-waves.

Heretofore the carbon F or its substitute has been placed upon the solid material of the base of the instrument; but I now place it upon a sensitive plane, and for this purpose I place the plate G, of thin resonant material- .glass, mica, iron, &c.--in the base of the instrument, firmly securing it thereto by one or more of its edges, and I mount the carbon F upon the same at a distance from its point of support.

The adjusting-screw D is prevented from revolving by means of a little pin projecting from its side into a groove cut in the head. The nut alone revolves.

The plate G, I prefer to make in circular form, and secure it at its edges all around; but good results may also be obtained if said plate is only secured at one of its edges.

I claim In an acoustic telegraph, the needle E, suspended upon an elastic support, 0, combined with a thin plate, G, of suitable elastic ma terial, substantially as and for the purpose set forth.

JOHN H. IRWIN.

Witnesses:

R. D. 0. SMITH, L. F. Burrs. 

